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diff --git a/docs/sources/zebra-multipath.md b/docs/sources/zebra-multipath.md new file mode 100644 index 00000000..fd71e3b5 --- /dev/null +++ b/docs/sources/zebra-multipath.md @@ -0,0 +1,205 @@ +# Equal Cost Multipath Routing with Zebra + +This page explains how GoBGP handles Equal Cost Multipath (ECMP) routes with +Zebra daemon included in [Quagga](http://www.nongnu.org/quagga/) or +[FRRouting](https://frrouting.org/). + +## Prerequisites + +Assume you finished [Getting Started](getting-started.md) and +[FIB manipulation](zebra.md). + +## Contents + +- [Configuration](#configuration) +- [Verification](#verification) + +## Configuration + +**Note:** Before constructing your environment, please confirm your Zebra is +built with "--enable-multipath=ARG" configure option. The APT packaged Quagga +on Ubuntu 16.04 is configured with this option as following. + +```bash +$ /usr/lib/quagga/zebra --version +zebra version 0.99.24.1 +Copyright 1996-2005 Kunihiro Ishiguro, et al. +configured with: + --build=x86_64-linux-gnu ...(snip)... --enable-multipath=64 ...(snip)... +``` + +Here supposes the following topology and demonstrates two ECMP routes which +advertised from R2 and R3 are installed to R1's Kernel routing table via Zebra. + +```text +R1: GoBGP + Zebra +R2: GoBGP +R3: GoBGP + + +-------------+ +-------------+ + | R1 | .1/24 .2/24 | R2 | + | ID: 1.1.1.1 |---------------------| ID: 2.2.2.2 | + | AS: 65000 | 192.168.12.0/24 | AS: 65000 | + +-------------+ +-------------+ + | .1/24 + | + | 192.168.13.0/24 + | + | .3/24 + +-------------+ + | R3 | + | ID: 3.3.3.3 | + | AS: 65000 | + +-------------+ +``` + +To enables ECMP features at GoBGP on R1, please confirm "use-multiple-paths" +option is configured as following. With this option, GoBGP will redistribute BGP +multipath routes to Zebra and Zebra will install them into Kernel routing table. + +```toml +# gobgpd.toml on R1 + +[global.config] + as = 65000 + router-id = "1.1.1.1" + +[global.use-multiple-paths.config] + enabled = true + +[[neighbors]] + [neighbors.config] + neighbor-address = "192.168.12.2" + peer-as = 65000 + [[neighbors.afi-safis]] + [neighbors.afi-safis.config] + afi-safi-name = "ipv4-unicast" + [[neighbors.afi-safis]] + [neighbors.afi-safis.config] + afi-safi-name = "ipv6-unicast" + +[[neighbors]] + [neighbors.config] + neighbor-address = "192.168.13.3" + peer-as = 65000 + [[neighbors.afi-safis]] + [neighbors.afi-safis.config] + afi-safi-name = "ipv4-unicast" + [[neighbors.afi-safis]] + [neighbors.afi-safis.config] + afi-safi-name = "ipv6-unicast" + +[zebra.config] + enabled = true + url = "unix:/var/run/quagga/zserv.api" + redistribute-route-type-list = ["connect"] + version = 2 +``` + +```toml +# gobgpd.toml on R2 + +[global.config] + as = 65000 + router-id = "2.2.2.2" + +[[neighbors]] + [neighbors.config] + neighbor-address = "192.168.12.1" + peer-as = 65000 + [[neighbors.afi-safis]] + [neighbors.afi-safis.config] + afi-safi-name = "ipv4-unicast" + [[neighbors.afi-safis]] + [neighbors.afi-safis.config] + afi-safi-name = "ipv6-unicast" +``` + +```toml +# gobgpd.toml on R3 + +[global.config] + as = 65000 + router-id = "3.3.3.3" + +[[neighbors]] + [neighbors.config] + neighbor-address = "192.168.13.1" + peer-as = 65000 + [[neighbors.afi-safis]] + [neighbors.afi-safis.config] + afi-safi-name = "ipv4-unicast" + [[neighbors.afi-safis]] + [neighbors.afi-safis.config] + afi-safi-name = "ipv6-unicast" +``` + +## Verification + +When connections established between each routers, all routers have only +"connected" routes from Zebra on R1. + +```bash +R1> gobgp global rib -a ipv4 + Network Next Hop AS_PATH Age Attrs +*> 1.1.1.1/32 0.0.0.0 00:00:00 [{Origin: i} {Med: 0}] +*> 192.168.12.0/24 0.0.0.0 00:00:00 [{Origin: i} {Med: 0}] +*> 192.168.13.0/24 0.0.0.0 00:00:00 [{Origin: i} {Med: 0}] + +R2> gobgp global rib -a ipv4 + Network Next Hop AS_PATH Age Attrs +*> 1.1.1.1/32 192.168.12.1 00:00:00 [{Origin: i} {Med: 0} {LocalPref: 100}] +*> 192.168.12.0/24 192.168.12.1 00:00:00 [{Origin: i} {Med: 0} {LocalPref: 100}] +*> 192.168.13.0/24 192.168.12.1 00:00:00 [{Origin: i} {Med: 0} {LocalPref: 100}] +``` + +And only these routes are installed on R1's Kernel routing table. + +```bash +R1> ip route +192.168.12.0/24 dev r1-eth1 proto kernel scope link src 192.168.12.1 +192.168.13.0/24 dev r1-eth2 proto kernel scope link src 192.168.13.1 +``` + +Then, let's add new routes destinated to "10.23.1.0/24" on R2 and R3 routes. +These routes should be treated as Multipath routes which have the same cost. + +```bash +R2> gobgp global rib -a ipv4 add 10.23.1.0/24 +R2> gobgp global rib -a ipv4 + Network Next Hop AS_PATH Age Attrs +*> 1.1.1.1/32 192.168.12.1 00:10:00 [{Origin: i} {Med: 0} {LocalPref: 100}] +*> 10.23.1.0/24 0.0.0.0 00:00:00 [{Origin: ?}] +*> 192.168.12.0/24 192.168.12.1 00:10:00 [{Origin: i} {Med: 0} {LocalPref: 100}] +*> 192.168.13.0/24 192.168.12.1 00:10:00 [{Origin: i} {Med: 0} {LocalPref: 100}] + +R3> gobgp global rib -a ipv4 add 10.23.1.0/24 +R3> gobgp global rib -a ipv4 + Network Next Hop AS_PATH Age Attrs +*> 1.1.1.1/32 192.168.13.1 00:10:00 [{Origin: i} {Med: 0} {LocalPref: 100}] +*> 10.23.1.0/24 0.0.0.0 00:00:00 [{Origin: ?}] +*> 192.168.12.0/24 192.168.13.1 00:10:00 [{Origin: i} {Med: 0} {LocalPref: 100}] +*> 192.168.13.0/24 192.168.13.1 00:10:00 [{Origin: i} {Med: 0} {LocalPref: 100}] +``` + +GoBGP on R1 will receive these routes and install them into R1's Kernel routing +table via Zebra. The following shows that traffic to "10.23.1.0/24" will be +forwarded through the interface r1-eth1 (nexthop is R2) or the interface r1-eth2 +(nexthop is R3) with the same weight. + +```bash +R1> gobgp global rib -a ipv4 + Network Next Hop AS_PATH Age Attrs +*> 1.1.1.1/32 0.0.0.0 00:15:00 [{Origin: i} {Med: 0}] +*> 10.23.1.0/24 192.168.12.2 00:05:00 [{Origin: ?} {LocalPref: 100}] +* 10.23.1.0/24 192.168.13.3 00:05:00 [{Origin: ?} {LocalPref: 100}] +*> 192.168.12.0/24 0.0.0.0 00:15:00 [{Origin: i} {Med: 0}] +*> 192.168.13.0/24 0.0.0.0 00:15:00 [{Origin: i} {Med: 0}] + +R1> ip route +10.23.1.0/24 proto zebra + nexthop via 192.168.12.2 dev r1-eth1 weight 1 + nexthop via 192.168.13.3 dev r1-eth2 weight 1 +192.168.12.0/24 dev r1-eth1 proto kernel scope link src 192.168.12.1 +192.168.13.0/24 dev r1-eth2 proto kernel scope link src 192.168.13.1 +``` |